Common easy open end closures for beer and beverage containers have a central or center panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “consumer side,” of the end closure. Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin sheet of aluminum or steel. End closures for such containers are also typically constructed from a cut-edge of thin sheet of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
One goal of the can end manufacturers is to provide a buckle resistant end. U.S. Pat. No. 7,350,392 and its related patents, publications, and pending applications describe a method aimed at improving the buckle strength of a can end having a seaming curl, a chuck wall. The method includes forming a fold along at least substantially the entire length of the chuck wall.
Some time ago, the art adopted a two-stage type of system for manufacturing can ends. The system uses a shell press that forms shells from a coil of stock material, and one or more end conversion presses that converts the shell into a finished end.
The presses known in the art generally fall into one of two categories: single action and double action presses. Single action presses use a single driving mechanism (ram device) to move the upper tool. Double action presses use two driving rams, an inner ram and an outer ram. Double action presses are considerably more complex and costly machines and are more expensive to maintain and operate.
Double action presses are described in, for example, U.S. Pat. No. 4,977,772 and U.S. Pat. No. 5,626,048, both of which are hereby incorporated by reference as if fully set forth herein. Typically, the upper portion of a double action tooling presses such as the one illustrated in FIG. 3 of the '772 patent, include an inner slide holder and an outer slide holder. The inner slide holder carries a stem secured thereto by one or more bolts. The projecting end of the stem carries a punch core secured thereto in adjustable fashion by the screw. In this fashion, the tooling such as punch core can be moved toward and away from the fixed base of the press as inner slide holder moves toward and away from the base.
The outer slide holder has an appropriate hollow cavity within which the stem and punch core of the inner slide holder reciprocate substantially independently of the movement of the outer slide holder.
This outer slide holder also carries with it certain tooling. First, radially inwardly is a sleeve secured thereto by retainer and screws so as to be reciprocal therewith. Radially outwardly of the sleeve and in concentric surrounding relationship therewith is a first pressure sleeve and a fluid actuated piston which acts thereon. Secured to the projecting bottom end of the outer punch holder is a cut edge which is secured by one or more screws.
The fluid actuated piston is carried by outer slide holder above first pressure sleeve and is controlled by fluid introduced through bore and vented through bore with bore being connected to a suitable source of fluid supply (not shown).
The outer slide holder will be moved to the down position and fluid pressure exerted on the piston through bore will force the first pressure sleeve into holding relationship with the material. Further downward movement of outer slide holder will cause the cut edge to blank the material against cut edge. In that regard, cut edge is carried on die holder and does not move. Stock plate is fluidly supported. Therefore, downward movement of cut edge will depress stock plate a sufficient distance to permit the blanking operation to take place.
Continued downward movement of the inner slide holder forces the punch core downwardly against the previously blanked material, pulling it out of its previously clamped position beneath sleeve and forming it into a shallow cup. The inner ram continues downwardly, while the outer slide holder is retracting.
As stated above, double action presses of this type are expensive to maintain and operate. Generally, the tooling in a double action press is difficult to access. This makes it difficult to align and guide the tooling.
Tramming the press is often difficult on a double action can end press. The upper tooling must be trammed to the lower tooling which is separated by the foot long stem.
There are also tooling wear issues in a double action press caused by galling. Galling occurs when there is contact between two tools, and a dull wear pattern develops on one or both tools. Galling can cause enough wear of the surface of a tool to the point where friction is created, and the tools seize up, restricting or eliminating tool movement.
There are also a great number of seals needed to operate a double action can end press. A large number of seals will create heat due to friction during operation. The excessive heat often causes tool control and guidance issues. When the tools fall out of alignment, the press will shear the cut edge of the metal stock. Shearing of the cut edge leads to defects in the seaming curl of the can end or in the later seaming process when the can end is seamed (attached) to a filled can body.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior double action can end presses of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.